A heat-sensitive recording sheet is produced by coating a compound capable of forming color upon application of heat, on a paper support. Various types of heat-sensitive recording sheets have been proposed.
For example, U.S. Pat. Nos. 3,666,525, and 4,471,074 disclose a heat-sensitive recording sheet using a combination of an electron-donating dye precursor and an electron accepting compound; U.S. Pat. Nos. 2,663,654 through 2,663,657 disclose a combination of the ferric salt of higher fatty acid and a polyhydric hydroxy compound; and U.S. Pat. Nos. 4,650,740, 3,695,885, and 4,411,979 disclose a heat-sensitive recording sheet using a combination of diazo sulfonate, a coupler and an alkaline substance. In addition, a system wherein azo, oxazine or formazane dyes are formed through the heat reaction of resorcinic acid and 3-nitro-5-methylsalicylic acid is known, as described in, for example, Japanese Patent Publication Nos. 18992/62 and 9240/63.
These heat-sensitive recording sheets are advantageous in that: (1) primary color-formation is employed and no development is needed, (2) the quality of the sheet is similar to that of the ordinary paper. and (3) handling is easy.
In recent years, such heat-sensitive recording sheets have been widely used in the fields of, e.g., facsimile machines, recorders and printers, and its demand is increasing.
Heat-sensitive recording as heretofore employed, comprised a recording system in which the recording speed is relatively slow. However, with an increase in the quality of a printing heat (i.e., a thermal head) and also an increase in the sensitivity of the heat-sensitive recording sheet, the recording speed has been greatly increased. However, with development of high speed recording, various problems have arisen. One of the problems is that static electricity is generated when the heat-sensitive recording sheet runs at a high speed, causing poor running such as jamming. This tendency is more marked under lower temperature and lower humidity conditions. The cause of these poor running tendencies is considered to be that when the heat-sensitive recording sheet runs at a high speed, friction is produced between the heat-sensitive recording sheet and a thermal head, a body or a platen roll, as a result of which static electricity is generated.